The goals of the projects are to develop thromboresistant surfaces based upon (1) controlled release of heparin incorporated into a surface layer of polymer and (2) controlled release of a platelet-inhibiting agent from a polymer layer. Physical incorporation is being used to imbed heparin into polymers to be used for coating. Present problems involve decreasing the final size of the heparin particles and increasing the time over which the heparin is released. Morphology control is the major tool being employed. Platelet inhibiting agents are being synthesized which are able to inhibit thrombin-induced platelet aggregation as well as ADP-induced aggregation. Various derivatives are being formed and tested for incorporation into polymer coatings. Baseline data on potential supports for the drug-releasing coatings show that high patency of vascular grafts requires a carefully defined surface geometry and porosity to permit growth of smooth thin neointima. In addition, anisotropy of the graft material enhances patency.